a. Field of the Invention
The instant invention relates to smoking articles. More specifically, the instant invention relates to cigarettes.
b. Background Art
In 2005, the European Commission established maximal values for “tar” (10 mg), nicotine (1 mg), and carbon monoxide (CO; 10 mg) per cigarette or “10-1-10,” as measured by the International Organization for Standardization (ISO) method, from 1 Jan. 2004. This is part of a trend of lower product yield for all smoke compounds delivered in the cigarette that entails developing new cigarette designs of lower yields while maintaining product taste and acceptability.
It is well known that smoking articles, particularly conventional filtered or unfiltered cigarettes, provide an increasing per puff yield of particulate matter (“puff-to-puff yield”) as the cigarette is smoked. In the past, high-efficiency filters and air dilution have been used to provide a lower total yield of particulate matter in the so-called “low tar” and “ultra-low tar” cigarettes now available in the marketplace. However, manufacturers find that high-efficiency filters significantly increase the pressure drop of the cigarette and decrease yield, especially in the first few puffs of the cigarette.
Likewise, air dilution helps to reduce the pressure drop somewhat, but also further reduces the per puff yield in the first few puffs. In combination, high-filtration efficiency and air dilution configured in the conventional way in a cigarette not only produces the desired lower total yield, but also produces an undesirable per puff yield or puff profile of little yield in the first few puffs and a high yield in the final few puffs. The puff profile of this type of configurations is perceived by the smoker of a cigarette as of inconsistent taste characteristics, i.e., little or no taste in the first few puffs and a harsh and overbearing taste in the final few puffs.
The art has attempted to address this problem in several ways as discussed below. The proposed solutions, however, lack the ease of manufacturing required to scale up commercialization of tar-controlled delivery products.
For example, U.S. Pat. No. 8,240,315 B2 teaches about a smoking article that provides lower amounts of total particulate matter in a latter portion of its puff count. The smoking article includes a cylinder of smoking material, a combustible hollow tube within the cylinder of smoking material, and a heat sink at a downstream end of the hollow tube. The smoking article also includes a filter system attached to the cylinder of smoking material having a sorbent material and at least one downstream segment of filtering material.
U.S. Pat. No. 8,235,057 B2 teaches about a smoking article which includes a tobacco rod adapted to produce mainstream smoke, and a filter having an upstream end and a downstream end, wherein the filter is arranged to receive mainstream smoke at the upstream end. The filter includes a tubular segment open at the downstream end thereof and a flow restrictor contained within the tubular segment. The filter is attached to the tobacco rod with tipping paper and includes an air-admissible ventilating zone at a location between the upstream end and the downstream end of the filter.
United States patent application publication no. 2008/0216851 A1 proposes to include a smokable filler of a smoking article with a high aerosol former content and a filter. Preferably, the smokable filler includes about 4 wt. % glycerin to about 35 wt. % glycerin. The filter includes a cylindrical tube attached to the tobacco rod with tipping paper, a first filter segment at a location along said cylindrical tube adjacent and in a downstream relation to said tobacco rod, and a flow restricting filter segment at a location adjacent and in a downstream relation to the first filter segment. In an embodiment, the filter also includes a cavity adjacent and in a downstream relation to the flow restricting filter segment, and a ventilation zone at a location along the cavity including perforations that extend through the tipping paper and the cylindrical tube. Preferably, the ventilation zone is in a downstream relation to the flow restricting filter segment.
United States patent application publication no. 2007/0186945 A1 teaches about a smoking article, which provides lower amounts of total particulate matter in a latter portion of its puff count, which includes a cylinder of smoking material, a combustible hollow tube within the cylinder of smoking material, and a heat sink at a downstream end of the hollow tube. The smoking article also includes a filter system attached to the cylinder of smoking material having a sorbent material and at least one downstream segment of filtering material.
U.S. Pat. No. 5,435,326 proposes a smoking article which has a controlled yield of wet particulate matter and a method of making a smoking article with predetermined total and per puff yields of wet particulate matter. The smoking article has a tobacco rod connected to an air ventilated compound filter having two abutted filter segments, a rod end segment with a passage therethrough and a mouth end segment. The pressure drop of the abutment interface between the segments is selected to be in a range of from about 10 mm to about 100 mm water gauge. According to this patent, the total pressure drop of the filter including the interface and the amount of air dilution can be selected to provide a smoking article with a level per puff yield or a decreasing per puff yield.
Furthermore, U.S. Pat. No. 4,972,853 teaches about a cigarette filter rod element that includes an axially-extending barrier tube of micro-fine fibers with a diameter of between 0.5 and 10 microns and located so that at least part of the gas flow passes through the wall of said barrier tube. U.S. Pat. No. 4,942,887 teaches about tobacco containing cigarette filter plugs that comprise strands of tobacco material which are bound with an activated binding agent. According to the '887 patent, the filter-plugs exhibit good firmness and integrity, and provide cigarettes exhibiting a unique tobacco taste. Filter plugs are prepared by forming an intimate admixture of tobacco material and binding agent, forming rods, and activating the binding agent. U.S. Pat. No. 4,109,666 teaches about a filter tipped cigarette that also includes a cylindrical tobacco section and a cylindrical filter axially aligned therewith. The filter is comprised of an axially aligned tube extending from said tobacco section, a layer of filter material positioned circumferentially about said tube, and a diffuser adjacent an end of the tube for dispersing the smoke received from the tube prior to entering the smoker's mouth.
One of the major drawbacks from what is described in the '326 patent noted above is a limitation in filter construction which is relegated to 31 mm filter designs based on the components identified to achieve relative consistency from puff to puff. Specifically, the prior art teaches that at least a 17 mm cellulose acetate (CA) filter segment equipped with a 1.0-1.5 mm tube is necessary to combine with a traditional cellulose filter segment to achieve a desired effect. In addition, the prior art teaches that interfacial abutment pressure between the “functional” filter segment and the standard cellulose acetate must be greater than traditional pressures achievable on standard filter rod making equipment; and, therefore, the ability to manufacture functional filters at commercially relevant speeds is unlikely. To that end, the basis of the purported invention of the '326 patent relies on the fact the CA segment containing the tube be sufficiently long so that the primary flow of mainstream smoke travels through the 1.0-1.5 mm tube and not through the surrounding CA material. This is due to the pressure drop differences between the tube and the CA material, requiring long filter segments to achieve the effect. When the pressure drop difference between the capillary tube and the surrounding material are similar, the effect cannot be achieved. Therefore, shorter filter constructions such as 27 mm, 25 mm, and 21 mm filters are not possible using what is described in U.S. Pat. No. 5,435,326.
The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.